The present invention relates to an access conversion technique of prediction macroblock data which is used for decoding and encoding a motion picture, and more particularly, to an access conversion method and apparatus of prediction macroblock data output from a frame memory which is stored in a separate storage unit, and then read by an order appropriate for processing the following prediction macroblock.
Motion picture coding is a technology of compressing and restoring motion picture data using motion compensation prediction, discrete cosine transformation (DCT), and variable length coding (VLC).
FIG. 1 is a block diagram of a general motion picture decoder. A variable length decoder 10 receives variable-length-coded data and decodes it via a reverse process. An inverse DCT portion 20 converts decoded data of a frequency region into video data of a spatial region. A motion compensator 30 reads a macroblock corresponding to a motion vector from video data of a previous frame stored in a frame memory 40 and adds the read macroblock to inversely discrete cosine transformed data, to thereby output motion picture data which is motion-compensated and restored.
Data compression of a motion picture is performed by DCT and VLC of a difference value between pictures. Considering movement of an inter-picture, a motion vector is found from a reference picture in units of a macroblock composed of Y of 16 pixels by 16 lines, U of 8 pixels by 8 lines and V of 8 pixels by 8 lines. Then, using a prediction macroblock of the position of the motion vector, a compression rate is enhanced, which is called a motion compensation prediction method.
In the motion compensation prediction method, prediction macroblock data is read from a frame memory, and the read prediction macroblock data is filtered via horizontal interpolation, vertical interpolation, forward prediction, and backward prediction.
However, since an order of reading prediction macroblock data from a frame memory does not match that of data which is used for a filtering process in a conventional motion picture decoding method, an access time of the prediction macroblock data is delayed.